It is often required to measure the torque in a shaft. For example, in the marine propulsion field it would be useful to know the shaft torque and shaft horsepower actually delivered to a propeller irrespective of engine speed. The applied torque gives rise to a circumferential twist on the shaft, the amount of twist being quite small and often difficult to measure. Stain gages are often employed on a shaft to produce an electrical signal which can be processed to provide an indication of torque. For a rotating shaft, however, the attachment of strain gages or other transducers is complicated by the necessity for coupling signals derived from the torqued shaft to external processing circuits.